Bokeh has been written about quite a bit, plenty on this site alone, but what is “perfect” Bokeh?
For me, from a working perspective, perfect Bokeh is a look that has the following characteristics;
It has to have clean separation of a sharp subject and soft background.
The background needs to be unobtrusive, but needs some definition for story telling.
The useable depth of field, and working distance need to be useable.
I have found lately, that all of these are easily achieved with my Olympus 25mm f1.8 (on any camera, but the Pen F or EM10 mk2 work well). For social events, I have been falling back heavily on the unassuming little EM10 and 25mm combo lately for portraits and other cameras and zooms for general shots.
Let’s look at the math of this combo.
In full frame terms you have the depth of field of a 24mm wide angle at f1.8,
but also,
in full frame terms, you have the perspective and magnification of a 50mm lens (closer to a 45 in this case, but near enough). The result is perceived of of two stops smaller for the magnification.
So you have in real terms a 50mm f2.8 equivalent. This is not often seen as shallow enough depth of field for most in this “Bokeh mad” time, but from a practical and more importantly, relevant way, it is ideal. I remember the 55mm f2.8 Micro Nikkor being a favourite back in the day. Also, a friend has a habit of shooting full frame 24mm f1.4 Bokeh portraits, using much the same math.
Practicality? Any shallower and groups of 2 or more people risk a face drifting out of best focus. F2.8 zooms are the work horse lenses for most full frame shooters, so f1.8 in M43 is no different.
Relevance? Shallower depth of field can create beautiful soft backgrounds, but also tend to blur out any environmental context. Context is important, otherwise you might as well take all of your shots in a hallway or studio.
Two of the adults (staff) attending a recent school event, they are nicely “cut” out of their background, both in good focus (and sharp), but their softer background is also coherent enough to tell a story (what, when, where). There were better examples, but they featured children and parents, so I will not use them. Processing was limited to a little colour balancing in C1 and are mostly in response to the slightly warm nature of the EM10’s sensor. The important elements here are a sense of place, with clearly defined main subjects.
If I had a f1.2 lens would I use it at f1.2? Likely not (after a short period of Bokeh love/lust that is). F1.2 is too shallow to trust in a working environment (studio’s aside) and would likely rob a shot of a feeling of being part of something.
The end result of this, is that I can set the lens to f1.8 for great light gathering, assured that I will always get a row of people sharp, but still soften the background nicely. The balance of elements is easily achieved and reassuring.